Gaseous sterilants are typically used for goods for which simple heat sterilization is not appropriate. For example, products containing heat-sensitive biological material in aqueous solution or in dry form, require sterilization at relatively moderate temperatures due to the thermal sensitivity of the materials involved. Packages containing proteins, steroids and vaccine components are examples. In such cases, the use of vacuum, steam and a gaseous sterilant is often an adequate solution. Gaseous sterilants in use include ethylene oxide, formaldehyde, peracetic acid and hydrogen peroxide. Ethylene oxide and formaldehyde are considered to be carcinogenic. Hydrogen peroxide is highly effective and has the advantage that its decomposition products are the relatively harmless substances oxygen and water.
Vaporized hydrogen peroxide (VHP) is used for decontamination and sterilization of enclosed and sealed areas. It is capable of destroying all forms of microbial life, including bacteria, bacterial spores, fungi, fungal spores, and viruses. It is commonly produced from a solution of liquid H2O2 and water, by means of generators specifically designed for the purpose. Aqueous hydrogen peroxide may be supplied as a 35% stabilized solution, for example Vaprox® supplied by STERIS Corporation.
VHP is used for loads that may be structurally fairly complex, containing voids or spaces. The loads often have low thermal conductivity, e.g. certain polymers. In these cases, uniform distribution of sterilant and temperature is of great importance.